The Black Art of Towing Part Four - Sway

Didn't Rosemary Clooney sing about sway? Probably not about trailer sway, though.

Trailer sway, more properly called "Yaw", is where your big heavy trailer behind you starts to oscillate around the towing ball and, if not checked, can have disastrous results. I did read a big academic study about trailer sway but you'd have to be a trailer nut like me to want to go through that so I'll just include this link here for further reading. It's really a commercial for the Hensley Arrow hitch but it's quite concise and easy to read. There is a notable exception to their causes of trailer sway in that they don't mention speed as a cause, however it's pretty good other than that. If you read further, you'll see that there are methods of controlling trailer sway and not all of them made by Hensley Manufacturing!

On our set up we use the simplest method of sway control and that is to dampen it with friction. We have a pair of sway control bars like the one pictured above (conveniently labelled "Sway Control"), one each side of the ball. They work by having one end connected to the trailer and the other to the hitch. Each bar has an arm that extends or retracts and the trailer pivots on the ball and by means of a pressure pad and some brake lining material, the arm's movement is restricted but not stopped completely. This dampens the side to side movement of the trailer and should a yaw situation occur then the pivoting action of the trailer is greatly restricted. 

I'd seen a similar application in steering dampers for motor cycles; the problem and the cure are identical. The friction method only dampens sway and there are other, more sophisticated methods that not only dampen but actually prevent sway by using opposite forces in the design of the hitch to counter the swaying movement. That said, even the no-sway hitches sometimes won't resist the force of a wildly swinging trailer and the hitch itself will fail, but fortunately that situation is unusual.

Despite having the least sophisticated system, albeit that we have two units operating, I've not had any sway issues when towing. When the big semis come past you can certainly feel the pull, but I'd not call that sway and I've never felt uncomfortable towing. That said, I'd never tow without sway control because no matter your trailer and no matter your tow vehicle, you will experience yaw if you don't do something to counter it.

In the next instalment I'll look at some of the other modifications made to the tow vehicle to help it in its towing duties. Watch this space....